CHAPTER 3 THE PERIODIC TABLE, ENGAGEMENT STRATEGIES AND
3.2 THE PERIODIC TABLE OF ELEMENTS
The PT was first invented in 1869 by Dmitri Mendeleev, a Russian chemist, to display the chemical elements known at that stage (Lengler & Eppler, 2007). The year 2019 was set apart as
‘’The International Year of the Periodic Table’’ for all chemists and scientists to commemorate 150 years of the PT (IUPAC, 2018).
The PT is described in many ways. It is considered a model, theory, representation, classification, and system by various scientists (Scerri, 2010; Brito et al., 2005). The PT in many books has classified the elements into main group and transition elements then further divided into subgroups A and B. However, the International Union of Pure and Applied Chemistry (IUPAC) recommends that the numbering of the main groups and transition elements starts from 1 to 18, meaning the PT should consist of 18 groups. This has gained acceptance and was adopted by many authors and chemists (Lee, 1996).
The properties of the electron structure of the chemical elements have been the focus for arranging the elements in groups within the PT. Over the years, chemists have arranged the elements in groups for two reasons, connecting the electron structure to the elements’ chemical properties and making the learning of the PT simpler (Lee, 1996). According to the IUPAC (2018);
there are 118 elements indicated on the IUPAC’s Periodic Table. It is worth mentioning that the 2016 IUPAC Periodic Table had 103 elements, but the current one (2018) has 118 elements. This implies that new elements have been discovered and added to the PT of the elements. The IUPAC(2018) version of the Periodic Table of elements indicates the 18 groups in Figure 3.1.
Figure 3-1: IUPAC Periodic Table of the Elements (IUPAC, 2018)
Nomenclature in the periodic table Names of groups of elements
The diagram below (Figure 3.2) shows the PT with the previous and current names of the various groups, adopted from (Lee,1996; 2008). The s-block and p-blocks on the PT were labelled under group I to VII and 0 according to the number of electrons in the outer shell of the atom, while the current IUPAC numbering of the groups is from 1 to 18. Elements are grouped by their chemical and physical properties.
Figure 3-2: Periodic Table of the previous and current names of the various groups The top row (IA-VIIB ) represents the previous group naming and the last row (1-18) the current grouping. The Russian chemist Dmitri Mendeleev published several tables with different arrangements of the chemical elements from 1869 to 1905. His Memorial Table, constructed in 1934, is based on atomic numbers in which both the inert gases and the lanthanoids are correctly placed (Laing, 2008). The IUPAC Periodic Table of Elements (Figure 3.1) is organised according to the element’s atomic numbers.
Comparing the atomic numbers and the groups of the first thirty elements of the Periodic Table of Elements
Table 3.1 displays the name, symbol, atomic number, and groups of the first 30 elements.
Table 3-1: Comparing the atomic numbers and groups on the Periodic Table
(Source: Author’s compilation)
Table 3.1 clearly shows that the atomic number of the elements does not always correspond with the group number. For instance, helium is an element with atomic number 2 but belongs to group 18, a noble gas and potassium has an atomic number of 19 which belongs to group 1, the alkali metals. The symbolic representation of the same elements is often derived from the first letter or two letters of the elements' name in English. For instance, carbon and argon are respectively represented as C and Ar, but potassium and sodium are K and Na, respectively.
Not all elements occur naturally. For instance, elements 104 through to 109 on the PT were formed using nuclear accelerators from accelerator laboratories in the United States, Germany
and Russia. Additionally, they radioactively decayed a few seconds after their birth. These artificial elements influence the classification of the elements on the PT.
A brief history of the Periodic Table classification
The system of classifying the Periodic Table elements started over 200 years ago (Scerri, 2011).
Over this time the PT has been subjected to robust changes in line with improved science and technological scientific research and findings. This has caused rejections, additions, alterations, confirmations, and improvement of the PT as new elements were discovered. The system for classifying the elements over these years was due to the concerted effort by many dedicated scientists.
Before Mendeleev’s work in 1869, other renowned scientists had carried out extensive research regarding the classification, description, and arrangement of some elements. For instance, in 1787, a French chemist, Antoine Lavoisier, in collaboration with Louis-Bernard Guyton de Morveau, Claude-Louis Berthollet and Antoine Fourcroy,, developed a listing for the 33 known elements using one-dimensional representations. However, the modern PT can be presented in two- or three-dimensional representations.
The contribution made by De Chancourtois in 1862 is recorded as a milestone in the development of the PT. De Chancourtois became the first to identify the characteristics of the elements as a role played by their atomic weight and represented the PT as a helical graphic system. In 1865, Newlands released his law of octaves which explains the repetition of chemical properties after a sequence of seven elements (Scerri, 2011; Brito et al., 2005; Van Spronsen,1969). From the 1870s, Mendeleev’s PT became easy to use for chemical lecturers and learners as it condensed a considerable amount of knowledge into meaningful connected facts, deleting isolated facts (Knight, 1998, xii).
History of naming selected elements
The International Union of Pure and Applied Chemistry (IUPAC) is a scientific body responsible for keeping a list of elements and unveiling the proposed names for comments, objections, and acceptance. IUPAC grew from other bodies such as the International Association of Chemical Societies (IACS). It was created in 1911 for international standardisation in chemistry. The same year (1911), IACS met in Paris and produced a set of proposals for the work of IUPAC. In 1892 the first international attempt to organise organic chemical nomenclature took place (Hepler- Smith, 2015).
The acceptance of new elements and names started with the submission of relevant literature on the discovered elements and fulfilling all the claims for discovery of the element(s) (Hofmann &
Münzenberg, 2000; Hofmann et al., 2018). This must be in line with the criteria for discovering the elements according to the IUPAP (International Union of Pure and Applied Physics), IUPAC and Transfermium Working Group (TWG) criteria. IUPAC and IUPAP, the Joint Working Party (JWP) are responsible for reviewing the literature and claiming of newly discovered elements.
Temporary names are given, and then the discoverer(s) are invited to submit permanent names.
The names are presented to scientists and the public for comments within five months and then finalised by IUPAC/IUPAP (Hofmann et al., 2018; Koppenol, 2002. Finally, the newly discovered elements with their atomic numbers, names, and symbols are included in the Periodic Table of Chemical Elements (PT).
In 1997, the names of six new chemical elements with their symbols were proposed to be confirmed by the members of the IUPAC union in Geneva. The names were, element 109, Meitnerium (Mt); element 104, Rutherfordium (Rf); element 105, Dubnium (Db); element 106, Seaborgium (Sg); element 107, Bohrium (Bh); element 108, Hassium (Hs), (Browne, 1997). They were approved and included to the Periodic Table of chemical elements.
The chemical elements were named after their places of discovery or scientists who played significant roles and contributions in their discovery. Thus, the element Bohrium is named after Niels Bohr for his influence on quantum physics. Hassium, after Hesse, the seat of the laboratory where elements 109 and 110 were created. Meitnerium is named after the Austrian physicist, Lise Meitner (Browne, 1997).
However, some elements were given provisional names but were rejected. For instance, Joliotium was assigned to element 105 after the French physicist Frederick Jolie-Curie. Hahnium (element 108) was named in honour of the German physicist Otto Hahn (Browne, 1997). Unfortunately, these names were not accepted and therefore not found on the current PT.
In 2011, about five more elements (elements 110, 111, 112, 114 and 116) were added to the PT.
Element 110 Darmstadtium (Ds) was named after the town in which it was discovered. Element 111 was named after the discoverer of X-rays, Wilhelm Conrad Roentgen. And Element 112 Copernicium (Cn) after the Polish astronomer Copernicus (Overbye, 2011). These names were given by the General Assembly of the International Union of Pure and Applied Physics (IUPAP) when they met in London, 2011. Interestingly, these elements do not last long once created and do not exist in nature (Overbye, 2011).
In addition, elements 114 and 116 were created in collaborative work of two organisations, namely:Lawrence Livermore National Laboratory in Livermore (Chang, 2011) and Institute for Nuclear Research in Dubna, Russia. Hence, names for elements 114 and 116 are flerovium (Fl) and livermorium (Lv) respectively. The names were subjected to scrutiny and analysis for acceptance within five months, after which they were finally recognised by an international committee of chemists and physicists in 2011. The chemistry union (IUPAC) then announced the accepted elements placed on the PT (IUPAC, 2018).
Four new elements were discovered and given temporary names, ununtrium (Uut), ununpentium (Uup), ununseptium (Uus) and ununoctium (Uuo) for elements 113,115, 117, and 118 respectively (St. Fleur, 2016; Karol et al., 2003; ). These elements were discovered by different groups from Japan, Russia, and USA. The teams that discovered the elements were given the chance to suggest names for elements 115 and 117. They named element 115 Moscovium, symbol Mc, after Moscow, and element 117, Tennessine (Ts) after Tennessee (St. Fleur, 2016; Karol et al., 2003).
Properties of the Periodic Table
The developmental stages associated with the history of the Periodic Table, according to Ben-Zvi and Genut, acknowledged a ‘constructivist’ way of scientific progress. However, as directly stated,
‘’PT is used in an 'empiricist' manner, especially in textbooks ‘’ (Ben-Zvi & Genut ,1998). This implies that PT used in textbooks depicts knowledge that is gained by observing, seeing, hearing, touching, or sensing things directly. Direct experience of the PT makes it easier to gain knowledge and understand the PT.
Knowledge of the Periodic Table reveals specific patterns of the element’s chemical properties and this is referred to as periodic trends. (Scerri, 2011). Examples of chemical properties are electronegativity, electron affinity, ionization energy and chemical reactivity. The physical properties on the other hand reveal the principles of periodicity and family or the group of which an element belong (Trudel & Métioui, 2015). Some examples of the physical properties are atomic number, density, state of matter, boiling and melting points.
Scerri (2019) maintains that quantum mechanics can explain the properties for classifying elements but not for hydrogen and helium and therefore proposed the continuous use of atomic number triads.
The structure and shape of the PT turn our focus on the columns, rows and blocks, which are a means of organising elements along two or three dimensions. The notion of valence contributed
significantly to determining the atomic masses and the grouping of elements in the columns.
Hence, rows and columns of the PT are important (Scerri, 2010).
Importance of the Periodic Table
The Periodic Table is one of the most valuable models in science (Scerri, 2019). It is of theoretical, practical, and educational importance to working scientists (Scerri, 2010; Brito et al., 2005), including teachers and educationists. The PT has a significant influence in the development of chemistry and physics (Scerri,1997:229;) and is a holistic part of chemistry (Scerri, 2010). The Periodic Table according, to Scerri, is ‘’the central concept in the study of chemistry’’ and a tool of utmost importance to modern chemists (Scerri,1998:78). From this viewpoint, the PT is an important instrument in modern chemistry and for modern chemists.
Scerri (2010) stated that the PT embodies all the elements and highlights all the layers of relationship among the elements. Harvey (2014) affirms that the PT is chemistry’s most emblematic image.
The learning of key concepts in chemistry is linked to understanding the structure and role of the PT (Trudel & Métioui, 2015). If an individual understands the structure and properties of the elements of the PT, the learning of key concepts such as the reactivity of chemical elements and reactions becomes easier. Therefore, the PT is crucial for understanding chemistry (Franco- Mariscal et al., 2017).
Though the Periodic Table is of fundamental importance to chemistry, learners in high school struggle to learn and understand the PT (Franco-Mariscal, Oliva-Martínez & Gil, 2015). This might be due to the fact that, learning the periodic table is not fun. This is affirmed by Franco-Mariscal et al., (2017) stating that gaining knowledge about the names and symbols of the chemical elements is an activity that learners frequently find boring (Franco-Mariscal et al., 2017).
Therefore, it is essential to identify strategies and resources that can provide opportunities to overcome difficulties and shortcomings in learning the PT (Franco-Mariscal et al., 2015).